The proposed work deals with the molecular organization of the neuromuscular junction. The major aim of our project is to localize and quantify the acetylcholine receptor (AChR) and acetylcholinesterase (AChE) at mouse and frog neuromuscular junctions, to study their normal turnover after denervation or inactivation with toxins, and to correlate the endplate morphology with functions as expressed in the time course of endplate currents.